1. Field of the Invention
The present invention relates to materials having high mechanical strength and corrosion resistance at high temperatures and heat resistance, which are reinforced with silicon carbide fibers and particularly to chromium base alloy composite materials reinforced with silicon carbide fibers.
Gas turbine using heavy oil of lower quality as fuel is heavily damaged by hot corrosion owing to vanadium oxide and sulfurous acid gas contained in combustion gas and for the purpose, super heat resistant alloys containing a large content of chromium have been used. However, as the chromium content in these alloys increases, the tensile strength at high temperatures lowers, so that the desired properties are not always fully satisfied.
2. Description of the Prior Art
As mentioned above, super alloys having a large content of chromium, such as 50Cr--50Ni, 50Cr--50Fe, 60Cr--40Co have been used under the severe condition wherein the corrosion and the oxidation at high temperatures proceed. However, chromium is more weak in the tensile strength at high temperatures than nickel, cobalt, molybdenum and the like, so that when it is intended to increase the corrosion resistance and the oxidation resistance, the tensile strength at high temperatures inconveniently lowers. Accordingly, it has been difficult to obtain materials having high corrosion resistance, oxidation resistance and tensile strength at high temperatures.
On the contrary, in this invention, chromium base alloy composite materials reinforced with silicon carbide fibers have been obtained with high tensile strength at high temperatures noticeably by using silicon carbide fibers without deteriorating the corrosion resistance and the oxidation resistance of chromium, and are very valuable as the heat resistant materials.